Each element \(\mathbf {E}_{h}\in \mathbf {V}_{h}^{\operatorname{edge}}(K)\)  is uniquely determined by the set
of constant values \((E_{e})_{e\in \mathcal {E}^{K}_{h}}\) , where
\(E_{e}=\mathbf {E}_{h}\cdot \mathbf {t}_{e}\)  is the tangential component of \(\mathbf {E}_{h}\) 
along the elemental edge \(e\) .
We take these values as the degrees of freedom of \(\mathbf {E}_{h}\)  and refer the
reader to [1]} for the
proof of their unisolvence in \(\mathbf {V}_{h}^{\operatorname{edge}}(K)\) .
A major consequence of such a space definition is that \(\Pi ^{0,K}_{0}\mathbf {E}_{h}\) 
is computable from the degrees of freedom of \(\mathbf {E}_{h}\)  for all
\(\mathbf {E}_{h}\in \mathbf {V}_{h}^{\operatorname{edge}}(K)\) .
